Contradirectional couplers

ABSTRACT

Contradirectional couplers for use in parallel-plate radial transmission line power dividers particularly suitable for use in phased array antenna systems. A plurality of contradirectional couplers are arranged in concentric rings in a first flat electrically conductive plate of a pair of parallel, spaced, flat, electrically conductive plates such that a power-coupling plate included in each coupler extends through an opening for a predetermined distance into the region between the two spaced plates. In a transmit mode of operation, a portion of the total power applied to the region between the spaced plates is coupled by each power-coupling plate included in each coupler, via a first electrical path through the coupler, to a corresponding load, for example, an antenna element. In the event any portion of the power coupled to a given antenna element is undesirably reflected back to the corresponding coupler, a major portion of such reflected power is absorbed by a load resistor provided in a second electrical path in the coupler. In a receive mode of operation, power received by the antenna elements from a target is coupled to the region between the parallel plates, via the first electrical paths through the couplers, and then applied to a suitable signal processing apparatus. A coaxial transmission line power divider embodying contradirectional couplers of a modified form is also disclosed.

United States Patent [72] inventor Leonard l. Parad Framingham. Mass. [211 App]. No. 860,339 [22] Filed Sept. 23, 1969 [45] Patented June 22, 1971 [73] Assignee Sylvania Electric Products, Inc.

[54] CONTRADIRECTIbNAL COUPLERS 15 Claims, 8 Drawing Figs.

[52] U.S. C1 333/10, 343/854 [51] 1ut.Cl 1101p 5/14 [50] Field oISearch 333/10; Mil/853,854

[56] References Cited UNITED STATES PATENTS 2,531,438 11/1950 Jones 333/10 X 2,764,739 9/1956 Fiet 333/10 3,092,790 6/1963 Leake et al. 333/10 3,416,102 12/1968 Hamlin 333/10 Primary Examiner-Herman Karl Saalbach Assistant Examiner-Paul L. Gensler TO LOAD AtrorneysOMalley, Norman, Elmer .1. Nealon and Peter Xiarhos ABSTRACT: Contradirectional couplers for use in parallelplate radial transmission line power dividers particularly suitable for use in phased array antenna systems. A plurality of contradirectional couplers are arranged in concentric rings in a first flat electrically conductive plate of a pair of parallel, spaced, flat, electrically conductive plates such that a powercoupling plate included in each coupler extends through an opening for a predetermined distance into the region between the two spaced plates. In a transmit mode of operation, a por tion of the total power applied to the region between the spaced plates is coupled by each power-coupling plate included in each coupler, via a first electrical path through the coupler, to a corresponding load, for example, an antenna element. In the event any portion of the power coupled to a given antenna element is undesirably reflected back to the corresponding coupler, a major portion of such reflected power is absorbed by a load resistor provided in a second electrical path in the coupler. in a receive mode of operation, power received by the antenna elements from a target is coupled to the region between the parallel plates, via the first electrical paths through the couplers, and then applied to a suitable signal processing apparatus.

A coaxial transmission line power divider embodying contradirectional couplers of a modified form is also disclosed.

LOAD

PATENIEU M2 2 I971 SHEET 3 BF 2 TO LOAD 69 COAXIAL OUTPUT CONNECTOR K =POWER COUPLING COEFFICIENT T0 CENTER OF RADIAL LINE POWER DIVIDER lf/f/ VLOAD RESISTOR V/l/ ///fl/ POWER COUPLING PLATE/ YER PMN ID wmm O TW K42 \PLATE lNVliN'IOR Fig LEONARD I. PARAD AGENT PATENTED JUN22 |97l 5 1 sum 3 OF 3 TO OUTPUT LOAD RESISTOR LOAD Z1 #51 Fig.

INVliN'I'OR LEONARD I. PARAD AGENT CONTRADIRECTIONAL COUPLERS BACKGROUND OF THE INVENTION The present invention relates to contradirectional couplers and, more particularly, to transmission line power dividers employing contradirectional couplers.

A phased array antenna system including a radial transmis' sion line power divider has been described in a copending patent application, Ser. No. 722,689, filed Apr. 19, 1968, in the names of Alfred J. Appelbaum, Peter R. Cloud, and Leonard l. Parad, and assigned to the same assignee as the present application. As described in detail in the above-mentioned applicatiomRF input power is applied during a trans mit mode of operation to a multimode hybrid launcher wherein a sum signal is generated and applied to the input port of a'radial transmission line power divider including a pair of spaced electrically conductive plates. The sum signal is divided by the radial transmission line power divider, at n output ports provided therein, into n output signals of reduced power level, and then coupled by means of coaxial transitions or probes located in the n output ports to an n:m stripline power divider.

The mm stripline power divider is so arranged as tofurther divide the n output signals from the radial line power divider into m signals of varying power levels and to route the m signals to m phase shifters associated with an array of m antenna elements. Each of the phase shifters operates under the control of a beam-steering control unit to insert a' differential phase shift in each. antenna element channel whereby a desired phase front is established across the aperture of the antenna array. in a receive mode of operation, signals received by the antenna array from a target are combined by the stripline power divider and the radial line power divider and applied for further processing to appropriate sum, elevation difference, and azimuth difference ports of the multimode hybrid launcher. f

Although the above-described system operates in a satisfactory manner to search and/or track a target, degraded operationmay occur-in the event a phase shifter or antenna element malfunctions or fails. Degraded operation may also occur during certain beam-forming operations. .For example, if a phase shifter or antenna element malfunctions or falls during the transmit mode of operation, a signal applied to the malfunctioning or failed phase shifter or antenna element by the radial line power divider may be undesirably reflected thereby and returned to the radial line power divider. Since the radial line power divider is not inherently capable of adequately dissipating the reflected signal, and since there is no inherent effective isolation present between the output ports provided therein, it is possible for the reflected signal to be coupled undesirably and unpredictably between the particular output port associated with the malfunctioning or failed phase shifter or antenna element and one or more of the remaining output ports and to be retransmitted to the corresponding antenna elements thereby causing errors in the energy distribution at the antenna aperture. The effect of these errors is to degrade the antenna sidelobes and to cause the main beam to squint.

Another source of possible error in the energy distribution at the antenna aperture in the above-described system may be caused when the phase across the antenna aperture is adjusted for form a beam which is steered far from broadside (usually BRIEF SUMMARY OF THE INVENTION Briefly, a coupler device is provided in accordance with a first embodiment of the invention for coupling electromagnetic energy from a region between a pair of spaced electrically conductive plates and for conducting the energy to a load, and for dissipating a major portion of unwanted electromagnetic energy reflected by the load. The coupler device in accordance with the first embodiment of .the invention comprises an electromagnetic energy transfer path means and an electromagnetic energy dissipating path means. The electromagnetic energy transfer path means is adapted to be connected to the load and includes an energy-coupling member disposed in the region between the pair of spaced electrically conductive plates. The electromagnetic energy dissipating path means includes the aforementioned electromagnetic energy transfer path means and a dissipating means connected in series with the energy-coupling member included in the electromagnetic energy transfer path means. In the operation of the above-described coupler device, electromagnetic energy present in the region between the pair of spaced electrically conductive plates is extracted therefrom by the electromagnetic energy transfer path means (which includes the energycoupling member), and conductedto the load. In the event any electromagnetic energy is reflected undesirably by the load, for example, due to a failure or malfunction in the load,

-such reflected energy is conducted along the electromagnetic energy transfer path means and through the energy-coupling member to the dissipating means. A major portion of the reflected energy is dissipated in the dissipating means.

A second coupler device in accordance with a second embodiment of the invention is also provided for extracting electromagnetic energy from a region between a pair of concentric, electrically conductive cylinders and for conducting the energy to a load, and for dissipating a major portion of unwanted electromagnetic energy reflected by the load. The

coupler device in accordance with the second embodiment of the invention includes an electrically conductive cylindrical coupling member provided with first and second spaced electrical terminal means, and which is adapted to be supported in the region between the pair of spaced electrically conductive concentric cylinders and concentric therewith. A first electrical path means is provided in series with the first electrical terminal means and the load, and a second electrical path means is provided in series with the second electrical terminal means. The second electrical path means includes a dissipating means therein for dissipating electromagnetic energy applied thereto. In the operation of the coupler device in accordance with the second embodiment of the invention, the electrically conductive member and the first electrical path means operate to extract and conduct electromagnetic energy from the region between the pair of electrically conductive cylinders to the load without application of a significant amount of energy to the second electrical path means or to the dissipating means included therein. In the event any unwanted electromagnetic energy is reflected undesirably by the load, the first electrical path means, the electrically conductive cylindrical coupling member, and the second electrical path means operate to conduct a major portion of the reflected electromagnetic energy to the dissipating means whereby such major portion of the reflected electromagnetic energy is dissipated in the dissipating means.

Also in accordance with the present invention, an apparatus is provided for transferring input electromagnetic energy to a plurality of output loads for subsequent transmission in a transmit mode of operation and for processing electromagnetic energy received by the output loads in a receive mode of operation, and for dissipating electromagnetic energy reflected undesirably by the output loads. The instant apparatus includes a first electrically conductive member having a plurality of openings provided therein in a predetermined pattern, and a second electrically conductive member spaced from the first electrically conductive member. The first and second electrically conductive members are so arranged as to receive in the region therebetween the input electromagnetic energy to be applied to the output loads. A plurality of coupler devices are arranged in the plurality of openings provided in the first electrically conductive member, one coupler device corresponding to each output load, and each adapted to be connected to a corresponding output load. Each of the coupler devices includes an electrically conductive coupling member which is provided with first and second spaced electrical terminal means and which is supported in the region between the first and second electrically conductive members. A first electrical path means is provided in series with the first electrical terminal means and the corresponding output load, and a second electrical path means is provided in series with the second electrical terminal means. The second electrical path means includes a dissipating means for dissipating electromagnetic energy applied thereto.

In the operation of the above-described apparatus during the transmit mode, the electrically conductive coupling member and the first electrical path means of each coupler device operate to extract and conduct electromagnetic energy from the region between the first and second electrically conductive members to the associated output load without application of a significant amount of electromagnetic energy to the second electrical path means or to the dissipating means included therein. In the receive mode of operation, the electrically conductive coupling member and the first electrical path means operate to conduct substantially all of the electromagnetic energy received by the associated output load during the receive mode of operation to the region between the first and second electrically conductive members. In the event any unwanted electromagnetic energy is reflected undesirably by an output load, for example, due to a failure or malfunction in the load, or due to mutual coupling efi'ects, the first electrical path means, the electrically conductive coupling member, and the second electrical path means operate to conduct a major portion of the reflected electromagnetic energy to the dissipating means whereby such major portion of the reflected electromagnetic energy is dissipated in the dissipating means.

As will be described in detail hereinafter, the first and second electrically conductive members of the abovedescribed apparatus may be flat or, alternatively, cylindrical, and the electrically conductive coupling member may be flat (corresponding to flat electrically conductive members) or cylindrical (corresponding to the cylindrical electrically conductive members).

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an exploded view in perspective of a contradirectional coupler in accordance with a first embodiment of the invention;

FIGS. 2, 3, and 4 are top, side, and front views, respectively, of the contradirectional coupler of FIG. 1, in assembled form;

FIG. 5 is a perspective view of a parallel-plate radial transmission line power divider in accordance with the present invention, employing a plurality of concentric rings of contradirectional couplers of the type shown in FIGS. 1 to 4;

FIG. 6 is an elevational view, partly in cross section of a single contradirectional coupler of the parallel-plate radial transmission line power divider shown in FIG. 5;

FIG. 7 is an elevational cross-sectional view, partly in schematic diagram form, of a portion of a coaxial transmission line power divider employing a contradirectional coupler in accordance with a second embodiment of the invention; and

FIG. 8 is an end view of the portion of the coaxial transmission line power divider shown in FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION CONTRADIRECTIONAL COUPLER- CONSTRUCTIONFIGS. 1-4

Referring to FIG. 1, there is shown in an exploded perspective view a contradirectional coupler l in accordance with a first embodiment of the invention. The contradirectional coupler 1 shown in FIG. 1 generally comprises: a pair of opposing, flanged metal plates 2 and 3; a first flat dielectric plate 4; a second flat dielectric plate 5 having a first portion 5a and a second, smaller portion Sb integral with the portion 5a; a stripline impedance-matching transformer arrangement 6 disposed on the second dielectric plate 5 between and integral with a contact 7 and a conductor 8; a stripline impedance-andload-matching arrangement 9 disposed on the second dielectric plate 5 in series with a load resistor 12 and also in series and integral with a conductor 10; a flat, thin, metal powercoupling plate 13 having a first pair of metal tabs 14a and a second pair of metal tabs 14b (shown in dotted outline) secured thereto; and a coaxial output connector 15 including a thin, metal contact 25.

The stripline impedance-matching transformer arrangement 6 comprises two conventional, integral, quarterwavelength impedance-matching transformer sections 611 and 6b the purpose of which is to impedance match the value of the impedance looking in the direction of the power-coupling plate 13, also of a quarter-wavelength, to the value of the characteristic impedance of the coaxial output connector 15. By way of a specific example, for an impedance of approximately I ohms looking in the direction of the powercoupling plate 13 and a typical characteristic impedance of 50 ohms for the coaxial output connector 15, the quarterwavelength impedance-matching transformer section 6a has a width of approximately 0.15 inch and provides approximately 60 ohms of impedance, and the quarter-wavelength impedance-matching transformer section 6b has a width of approximately 0.02 inch and provides approximately 130 ohms of impedance. As will be appreciated by those skilled in the art, for a different impedance looking in the direction of the power-coupling plate 13 and/or for a different characteristic impedance for the coaxial output connector 15, the values of the widths of the quarter-wavelength impedance-matching transformer sections 6a and 6b will be different from the specific values given in the above example. Moreover, other alternative and equivalent impedance-matching arrangements and modifications will be apparent to those skilled in the art.

The stripline impedance-and-load matching arrangement 9 comprises a conventional quarter-wavelength impedancematching transformer section 9a and a pair of conventional load-matching elements 9b and 9c. The purpose of the quarter-wavelength impedance-matching transformer section 9a is to impedance match the value of the impedance looking in the direction of the power-coupling plate 13 to the value of the load resistor 12 which may be, for example, a deposited carbon film resistor. For the above-mentioned 190 ohm value for the impedance looking in the direction of the powercoupling plate 13, and assuming a value of approximately ohms for the load resistor 12, the quarter-wavelength impedance-matching transformer section 90 has a width of approximately 0.02 inch and provides approximately ohms of impedance.

The purpose of the load-matching elements 9b and 9c is to electrically short circuit the "open" end of the load resistor 12 (the end associated with the load-matching element 90) to RF ground and also to substantially eliminate any reactance inherently present in the load resistor 12 as a consequence of its manufacture, thereby providing an essentially resistive path from the load-matching element 9c to the power-coupling plate 13. The precise dimensions of the load-matching elements 9b and 9c are determined by triaI-and-error techniques as is well understood by those skilled in the art. Although a specific combination of a stripline impedance-and-load matching arrangement 9 and load resistor 12 is disclosed, it is to be appreciated that other alternative arrangements may be used. For example, the impedance-and-load matching arrangement 9 and the load resistor 12 may be replaced by an impedance-matching arrangement like that of the impedancematching arrangement shown at 6 and a suitable load resistor of appropriate value and an RF ground provided externally of the contradirectional coupler.

Some typical materials which may be employed in the construction of the contradirectional coupler 1 of FIG. 1 are as follows. The metal flanged side plates 2 and 3 may be of riainch thick aluminum plate, the power-coupling plate 13 and the metal tabs 14a and 14b may be of l/32-inch thick aluminum, the dielectric plates 4 and 5 may be of Az-inch thick polyethylene (e=2.3), and the stripline elements (designated in FIG. 1 by the'reference numerals 6-10) may be of 0.002 inch thick copper and formed on the dielectric plate 5 in accordance with well-known plating and etching techniques. The various components of the contradirectional coupler 1 are assembled in the manner indicated in FIG. 1. Various views of the assembled contradirectional coupler are shown in FIGS. 2-4.

As may be noted from FIG. .1, when the contradirectional coupler 1 is assembled, the thin, metal inner contact 25 provided in the coaxial output connector makes physical contact with the contact 7, and the load resistor 12 is conveniently housed within a cavity formed by rectangular aligned openings 30 and 31 provided in the dielectric plates 4 and 5, respectively, thereby resulting in an integral, flat, compact structure. Additionally, it is to be noted that when the contradirectional coupler l is assembled, the flanged side plates 2 and 3 have rear surfaces, designated in FIG. 1 by the reference numerals 35 and 36, respectively, which act as ground planes for the dielectric plates 4 and 5 and the stripline components 6-10.

contradirectional Coupler-Operation-FIGS. 1-4

Briefly, the operation of the single contradirectional coupler 1 shown in FIG. 1 is as follows. For purposes of the present discussion, it will be assumed that the power-coupling plate 13 and the portion 5b of the dielectric plate 5 are inserted into a confined region, for example, in the region between a pair of parallel electrically conductive plates such as shown in FIG. 6. Input power to be coupled to an external load (not shown) is applied to the region between the parallel plates (in front of the power-coupling plate 13) and is transferred along a power-transfer path including the powercoupling plate 13, the tab 14a making contact with the conductor 8, the conductor 8, the quarter-wavelength impedancematching sections 6a and 6b, the contact 7, and the contact 25, to the external load. It is to be particularly noted that very little of the power to be directed to the external load is applied to the load resistor 12. The precise reasons for this are not clearly understood at the present time; however, it is theorized that the incident field in front of the power-coupling plate 13, due to the input power, splits into two fields, one above the power-coupling plate 13 and one below the power-coupling plate 13. The bottom field travels below the power-coupling plate 13 and, at the end of the power-coupling plate 13, some of it couples into the region above the power-coupling plate 13. The top field and the portion of the bottom field coupled above the power-coupling plate 13 then tend to combine or add at the conductor 8 and to cancel at the conductor 10. The net result is that essentially all of the power in front of the power-coupling plate 13 is coupled to the external load and very little is coupled to the load resistor 12. A well-known mathematical analytical approach, by which the effects of even and odd excitations on the contradirectional coupler 1 can be examined, has also been employed to explain the above operation and to derive general design equations for the contradirectional coupler. Further discussion on this aspect will be presented hereinafter in connection with FIGS. 5 and 6.

In the event any of the incident powei' coupled to the external load is reflected thereby in a direction opposite to the direction of the incident power, for example, due to a malfunction or failure in the load, the greater portion of such reflected power (from 60-99 percent, depending on the power coupling coefficient of the coupler, to be discussed hereinafter) is applied to the load resistor 12 and dissipated therein. More particularly, the power-dissipating path for the reflected power includes the contact 25, the contact 7, the quarter-wavelength impedance-matching sections 6a and 6b, the conductor 8, the tab 14a making contact with the conductor 8, the power-coupling plate 13, the tab 14b making contact with the conductor 10, the conductor 10, the quarterwavelength impedance-matching section 9a, the loadmatching element 9b, the load resistor 12, and the loadmatching element 90. Any portion of the reflected power not dissipated in the load resistor 12, constituting leakage, is directed by the power-coupling plate 13 into the region in front of the power-coupling plate 13 and has no significant adverse effect on the operation of the coupler.

Radial Transmission Line Power Divider Construction-FIGS. 5 and 6 Referring now to FIGS. 5 and 6, there is shown a radial transmission line power divider 40 employing a plurality of contradirectional couplers of the type shown in FIGS. 1-4. As shown in FIG. 5, the radial transmission line power divider 40 includes a pair of flat, parallel, circular plates 41 and 42 spaced from each other at the'circumferences thereof by a cylindrical spacer 43, and a plurality of contradirectional couplers CC, each of the general configuration shown in FIGS. 1-4, and arranged in a plurality of concentric rings R,-R by insertion into a plurality of substantially equally spaced openings 44 provided in the plate 41. For the sake of simplicity in the drawing, only two contradirectional couplers CC are shown in each of the rings Il -R of couplers in FIG. 5. The parallel plates 41 and 42 and the cylindrical spacer 43 may be of Iii-inch aluminum. A typical spacing between'the openings 44 in the plate 41 is a 0.6 wavelength.

In addition to the rings R -R of contradirectional couplers CC, a plurality of conventional coaxial probes P, two of which are shown in FIG. 5, are arranged in an outermost ring R, in the plate 41 by insertion into the outermost ring of the openings 44 provided in the plate 41. The purpose of the ring R of coaxial probes P will be explained hereinafter. Input power to be divided by the radial transmission line power divider 40 into a plurality of individual output signals for driving a plurality of associated output loads is applied to the region between the parallel plates 41 and 42 via a centrally located opening 46 (shown in dotted outline) provided in the plate 42. Typically, the output loads may be antenna elements, or combinations of phase shifters or coaxial lines and antenna elements. As understood by those skilled in the art, stripline components may also be used in conjunction with the above-mentioned components where deemed appropriate or desirable. Thus, the radial transmission line power divider 40 of FIG. 5 is particularly suitable for use in linear and planar phased array antenna systems.

As shown in FIG. 6, each of the contradirectional couplers CC has a portion A which extends for a depth in into the region between the parallel plates 41 and 42. The particular value of the dimension 1: associated with each contradirectional coupler CC is related to the percentage of the total input power applied to the region intermediate to the plates 41 and 42 of radial line power divider'40 to be coupled out by the coupler to its associated load, and may vary from coupler to coupler. Generally speaking, the greater the value of h for a given coupler, the greater is the amount of the total input power coupled out by that coupler to its associated load, and vice versa. In this connection, however, it is to be noted that if couplers having several different values of h are employed, for each value of h of a coupler, a different impedance-matching condition exists between the power-coupling plate and the associated coaxial output connector. Thus, for the several couplers having different values of h, appropriate different impedance-matching arrangements should be provided within the couplers to effect optimum power transfer between the power-coupling plates and the coaxial output connectors, in the manner described, for example, the connection with the coupler 1 of FIG. 1. In addition, for different values of h, different shapes for the power-coupling plates have been found to be particularly desirable for most effective operation. For example, for a spacing of H=0.82 inch between the parallel plates 41 and 42, and for a value of h of 0.6 inch or greater, a multisided power-coupling plate, for example, as shown in FIG. 1 (eight sides), or, alternatively, a circular powercoupling plate (shown in dotted outline in FIG. 1), have been found to be particularly effective. For a value of h of 0.038 inch or less, rectangular or oval power-coupling plates have been found to be particularly effective.

Although, as suggested hereinabove, it is possible for the contradirectional couplers CC in a given ring to have different values of h, in a preferred form of the radial transmission line power divider 40 the couplers of a given ring all have the same value of h. However, the value of h may differ from ring to ring, the specific value of h for a given ring corresponding to the particular percentage of the total power applied to the region intermediate to the plates 41 and 42 of the power divider 40 it is desired that the ring of couplers couple out to the associated loads.

Although three rings R,R, of contradirectional couplers CC have been illustrated in FIG. 5, it is to be understood that a greater or lesser number of rings of couplers may be employed depending on the particular application. Additionally, configurations other than rings may be employed where deemed appropriate or desirable to achieve a particular energy distribution at the output loads.

Radial Transmission Line Power Divider OperationFlGS. 5 and 6 The operation of the radial transmission line power divider 40 of FIG. 5 to direct power in a transmit mode of operation to a plurality of loads, for example, antenna elements, and to receive power from the antenna elements in a receive mode of operation is as follows. Input power to be divided by the power divider 40 and then applied to the antenna elements in the transmit mode of operation is applied to the region intermediate to the parallel plates 41 and 42 via the opening 46 provided at the center of the plate 42. Each of the rings R, R of contradirectional couplers CC couples out to the associated antenna elements a fraction of the total power applied to the power divider 40, the particular fraction of the total power coupled out by each of the rings R,R being a function of the particular value of h corresponding thereto as discussed previously. The particular portion of the power received by each ring of couplers which is coupled out by each of the individual couplers in the ring depends on the number of couplers in the ring which is established by the radius of the ring (assuming an equal spacing between the couplers in the ring).

Most of the power applied to the rings R,R, of couplers CC is coupled to the associated antenna elements. However, due to inherent practical limitations of the couplers CC, the rings R,-'R of couplers CC are unable to couple out to the associated antenna elements all of the input power applied to the power divider 40. As a result, a certain, small portion of the input power escapes past the outer ring R of couplers CC and moves toward the peripheral edges of the plates 41 and 42. Inasmuch as it is not desirable in a highly efficient practical system to allow any portion of the input power to remain uncoupled in the region between the parallel plates 41 and 42, the ring R, of coaxial probes P is provided to couple out to associated antenna elements the small portion of the input power escaping past the outer ring R of couplers. It is to be appreciated, however, that for certain system applications not requiring very high operating efficiency, the ring R, of coaxial probes P may be omitted or replaced by an internal load or loads of dissipative material.

The output signal, that is, the power produced at the coaxial output connector of each of the contradirectional couplers CC, is applied to the associated antenna element and directed to a target in a well known manner. In the event any of the power applied to a given antenna element is reflected back to the corresponding contradirectional coupler, due, for example, to a malfunction or a failure of the antenna element or due to undesirable mutual coupling effects, the major portion of such reflected power is dissipated in the load resistor included in the coupler in the manner previously described in connection with the contradirectional coupler 1 of FIG. 1. As a result, the reflected power is not coupled out to any of the other couplers back toward the antenna elements to cause errors in the energy distribution at the antenna aperture.

In the receive mode of operation, signals returned by the target in response to the transmitted beam are received by the antenna elements and applied to the associated contradirectional couplers CC and to the coaxial probes P. Each of the contradirectional couplers CC operates to transfer substantially all of the power received at its coaxial output connector from the associated antenna element to the region between the parallel plates 41 and 42 via an electrical path extending from the coaxial output connector to the powercoupling plate. Similarly, the power received by each of the coaxial probes P is transferred thereby to the region between the parallel plates 41 and 42. The power transferred by each of the contradirectional couplers CC and by each of the coaxial probes P radiates toward the center of the parallel plates 41 and 42 and combines at the center to produce a single signal at the opening 46 in the plate 42. Thus, in the receive mode of operation, the power divider 40 acts as a power combiner. The signal appearing at the opening 46 is then applied to and processed by suitable well-known signal-processing apparatus (not shown).

As may be noted from the above discussion, in the receive mode of operation, little of the power received by each of the contradirectional couplers is applied to and dissipated in the load resistor provided therein. Although the number and complexity of the operations simultaneously taking place within the power divider 40 during the receive mode of operation are too great to admit of a simple and straightforward explanation, the following, somewhat oversimplified explanation may aid in understanding why little of the power received by the contradirectional couplers is applied to and dissipated in the load resistors provided therein.

As a given contradirectional coupler in a given ring transfers the power received at its coaxial output connector to the associated power-coupling plate and then into the region between the parallel plates 41 and 42, it also seeks to transfer the power to its associated load resistor. However, at the same time, the power-coupling plate of the coupler is exposed to the power coupled into the region between the plates 41 and 42 by couplers in other rings and also by the coaxial probes, as the power coupled by the other couplers and probes converges toward the center of the plates 41 and 42. For example, the power-coupling plate of a coupler in the ring R; is exposed to power coupled into the region between the plates 41 and 42 by one or more of the coaxial probes P; similarly, the powercoupling plate of a coupler in the ring R, is exposed to power coupled into the region between the plates 41 and 42 by one or more of the couplers in the ring R; and also by one or more of the coaxial probes P; etc. The fields established in the vicinity of the coupler, resulting from the power sought to be applied to the load resistor of the coupler, are essentially of the same magnitude but opposite in phase to the fields resulting from the power coupled to the coupler from other couplers and/or coaxial probes. The net effect is that the fields efi'ectively cancel each other such that little of the power is applied to the load resistor. instead, substantially all of the power received by the coupler is transferred into the region between the plates 41 and 42. The above-described results appear to conform to and satisfy the well-known theorem of reciprocity commonly employed to explain the operation of many types of power divider/combiner arrangements.

Contradirectional Coupler General Design Equations Although specific contradirectional couplers have been illustrated in FIGS. land described in detail, and specific design details presented relating to their construction, both individually (FIGS. 1-4) and as employed in a radial transmission line power divider (H6. 5), certain general design equations may be derived as a result of mathematical analysis which apply to contradirectional couplers in accordance with the present invention and which, when suitably implemented, allow one to produce contradirectional couplers capable of providing effective power transfer and signal isolation. More particularly, these design equations, which can be derived as a result of a mathematical, analytical approach known as odd and even excitations" by which the effects of odd and even excitations on a contradirectional coupler may be examined, are given as follows, referring to FIG. 6,

where R is the impedance looking from the impedancematching transformers toward the power-coupling plate, Z is the characteristic impedance between the parallel plates 41 and 42 (outside of the power-coupling region), Z, is the characteristic impedance between the power-coupling plate and the plate 41, 2 is the characteristic impedance between the power-coupling plate and the plate 42, and K is a power coupling coefficient representing the portion of the power in the region between the parallel plates 41 and 42 coupled out by the contradirectional coupler. By way of an example, for a 6db. coupler, K has a value of Modified Contradirectional Coupler FIGS. 7 and 8 Referring to FIGS. 7 and 8, there is shown, partly in schematic form and in cross section, a portion of a coaxial transmission line power divider 50 embodying a modified contradirectional coupler 55. As shown in F IGS. 7 and 8, the contradirectional coupler 55 comprises a quarter-wavelength, cylindrical power-coupling member 56 encircling an inner cylindrical coaxial conductor 57, and a pair of electrical paths 58 and 59, shown in schematic form, extending from the opposite ends of the power-coupling member 56 and passing through respective openings 60 and 61 provided in an outer cylindrical coaxial conductor 62. Preferably, the outer cylindrical coaxial conductor 62 has an increased diameter in the coupling region generally indicated at 62a.

The electrical path 58 in H6. 7 corresponds to the powertransfer path provided between the powercoupling plate 13 and the coaxial output connector of the contradirectional coupler l of FIG. 1, and the electrical path 59 corresponds to the power-dissipating path (including the power-dissipating load resistor) provided between the power-coupling plate 13 and the load-matching element 9b of the contradirectional coupler l of FIG 1. The electrical paths 58 and 59 of the contradirectional coupler 55 may be implemented in any suitable manner. Although not shown in FIGS. 7 and 8, the inner coaxial conductor 57 is typically spaced from the outer coaxial conductor 62 by means of conventional dielectric spacers, for

example, polyethylene spacers, provided at both ends of the coaxial conductors 57 and 62. The dielectric in the regions and -71 between the coaxial conductors 57 and 62, and between the power-coupling member 56 and the coaxial conductor 57, respectively, may be air or, alternatively, polyethylene. Although only one contradirectional coupler 55 is shown in FIGS. 7 and 8, it is to be appreciated that several contradirectional couplers are normally used, the diameters of the cylindrical power-coupling members of the various couplers being varied to achieve the desired power division.

As indicated in FIG. 7, the design equations that apply to the contradirectional couplers of FIGS. 1-6 also apply to the contradirectional coupler 55. In the case of the contradirectional coupler 55, R is the impedance looking toward the power-coupling member 56, Z, is the characteristic impedance of the coaxial transmission line (outside of the power-coupling region), Z is the characteristic impedance between the power-coupling member 56 and the coaxial conductor 62, Z; is the characteristic impedance between the power-coupling member 56 and the coaxial conductor 57, and K is, as before, the power coupling coefficient What I claim is:

l. A device for extracting electromagnetic energy from a region between a pair of concentric, electrically conductive cylinders and for conducting the energy to a load, and for dissipating a major portion of unwanted electromagnetic energy reflected by the load, comprising:

an electrically conductive cylindrical coupling member supported in the region between the pair of spaced electrically conductive concentric cylinders and concentric therewith, and having first and second spaced electrical terminal means;

first electrical path means in series with the first electrical terminal means and the load; and

second electrical path means in series with the second electrical terminal means and including a dissipating means for dissipating electromagnetic energy applied thereto;

said electrically conductive cylindrical coupling member and said first electrical path means being operable to extract and conduct electromagnetic energy from the region between the pair of electrically conductive cylinders to the load without application of a significant amount of energy to the second electrical path means or to the dissipating mean included therein; and

said first electrical path means, said electrically conductive cylindrical coupling member, and said second electrical path means being operable to conduct a major portion of any electromagnetic energy reflected undesirably by the load to the dissipating means whereby such major portion of the reflected electromagnetic energy is dissipated in the dissipating means.

2. A device in accordance with claim 1 wherein the dissipating means is a resistive load element.

3. Apparatus for transferring input electromagnetic energy to a plurality of output loads for subsequent transmission in a transmit mode of operation and for processing electromagnetic energy received by said output loads in a receive mode of operation, and for dissipating electromagnetic energy reflected undesirably by said output loads, comprising:

a first electrically conductive member having a plurality of openings provided therein in a plurality of groups each arranged around a common axis, each of said groups of openings having a number of openings differing from the number of openings of other groups;

a second electrically conductive member spaced from the first electrically conductive member;

said first and second electrically conductive members being arranged to receive in the region therebetween the the input electromagnetic energy;

a plurality of coupler devices arranged in the plurality of openings provided in the first electrically conductive member, one coupler device corresponding to each output load, and each adapted to be connected to a corresponding output load, each of said coupler devices comprising:

an electrically conductive coupling member supported in the region between the first and second electrically conductive members and having first and second spaced electrical terminal means;

first electrical path means in series with the first electrical terminal means and the corresponding output load; and

second electrical path means in series with the second electrical terminal means and including a dissipating means for dissipating electromagnetic energy applied thereto;

said electrically conductive coupling member and said first electrical path means being operable to extract and conduct electromagnetic energy from the region between the first and second electrically conductive members to the associated output load during the transmit mode of operation without application of a significant amount of electromagnetic energy to the second electrical path means or to the dissipating means included therein, and said electrically conductive coupling member and said first electrical path means being operable to conduct substantially all of the electromagnetic energy received by the associated output load during the receive mode of operation to the region between the first and second electrically conductive members; and

said first electrical path means, said electrically conductive coupling member, and said second electrical path means being operative to conduct a major portion of any electromagnetic energy reflected undesirably by the corresponding output load to the dissipating means, whereby such major portion of the reflected energy is dissipated in the dissipating means.

4. An apparatus in accordance with claim 3 wherein each electrically conductive coupling member is a flat, rnultiedged element.

5. An apparatus in accordance with claim 3 wherein each electrically conductive coupling member is a flat member having a circular configuration.

6. An apparatus in accordance with claim 3 wherein the first and second electrically conductive members are fiat members and each of the electrically conductive coupling members is a flat member.

7. An apparatus in accordance with claim 3 wherein the first electrical path means in each coupler device includes:

an output connector adapted to be connected to the associated output load; and an impedance-matching arrangement connected between the first electrical terminal means of the electrically conductive coupling member and the output connector for impedance matching the value of the impedance looking in the direction of the coupling member to the value of the characteristic impedance of the output connector. 8. An apparatus in accordance with claim 7 wherein the impedance-matching arrangement includes impedance matching transformer sections.

9. An apparatus in accordance with claim 8 wherein: the dissipating means included in the second electrical path means in each coupler device is a resistive load element; and wherein the second electrical path means further includes:

an impedance-matching arrangement in series with the second electrical terminal means of the electrically conductive coupling member and the resistive load element for impedance matching the value of the impedance looking in the direction of the electrically conductive coupling member to the value of the resistive load element.

10. An apparatus in accordance with claim 9 wherein the impedance-matching arrangement includes an impedancematching transformer section.

11. An apparatus in accordance with claim 10 further comprising:

means associated with the first and second electrically conductive members for removing from the region between the first and second electrically conductive members any electromagnetic energy not extracted and conducted to associated output loads by the plurality of coupler devices.

12. An apparatus in accordance with claim 10 wherein the second electrical path means in each coupler device further includes:

a load-matching arrangement in series with the resistive load element for establishing an RF ground for the resistive load element and for eliminating substantially any reactance inherently present in the resistive load element.

13. An apparatus in accordance with claim 12 wherein:

the impedance-matching arrangement included in the first electrical path means and the impedance-matching arrangement and the load-matching arrangement included in the second electrical path means are formed from stripline components; and

each coupler device further comprises:

first and second flat opposing dielectric members arranged to enclose between opposing surfaces the stripline components; and

first and second ground plane members in physical contact with the other surfaces of the first and second dielectric members, respectively.

14. Apparatus for transferring input electromagnetic energy to a plurality of output loads for subsequent transmission in a transmit mode of operation and for processing electromagnetic energy received by said output loads in a receive mode of operation, and for dissipating electromagnetic energy reflected undesirably by said output loads, comprising:

a first hollow, cylindrical, electrically conductive member having a plurality of openings provided therein in a predetermined pattern;

a second hollow, cylindrical, electrically conductive member concentric with the first electrically conductive member;

said first and second electrically conductive members being arranged to receive in the region therebetween the input electromagnetic energy;

a plurality of coupler devices arranged in the plurality of openings provided in the first electrically conductive member, one coupler device corresponding to each output load, and each adapted to be connected to a corresponding output load, each of said coupler devices comprising:

a hollow, cylindrical electrically conductive coupling member supported in the region between the first and second electrically conductive members and concentric with the first and second electrically conductive members, said electrically conductive coupling member having first and second spaced electrical terminal means;

first electrical path means in series with the first electrical terminal means and the corresponding output load; and

second electrical path means in series with the second electrical terminal means and including a dissipating means for dissipating electromagnetic energy applied thereto;

said electrically conductive coupling member and said first electrical path means being operable to extract and conduct electromagnetic energy from the region between the first and second electrically conductive members to the associated output load during the transmit mode of operation without application of a significant amount of electromagnetic energy to the second electrical path means or to the dissipating means included therein, and said electrically conductive coupling member and said first electrical path means being operable to conduct substantially all of the electromagnetic energy received by the associated output load during the receive mode of operation to the region between the first and second electrically conductive members; and

said first electrical path means, said electrically conductive coupling member, and said second electrical path means being operative to conduct a major portion of any electromagnetic energy reflected undesirably by the corresponding output load to the dissipating means, whereby such major portion of the reflected energy is dissipated in the dissipating means.

15. Apparatus for transferring input electromagnetic energy to a plurality of output loads for subsequent transmission in a transmit mode of operation and for processing a electromagnetic energy received by said output loads in a receive mode of operation, and for dissipating electromagnetic energy reflected undesirably by said output loads, comprising:

a first electrically conductive member having a plurality of openings provided therein in a plurality of concentric rings;

a second electrically conductive member spaced from the first electrically conductive member;

said first and second electrically conductive members being arranged to receive in the region therebetween the input electromagnetic energy;

a plurality of coupler devices arranged in the plurality of openings provided in the first electrically conductive member, one coupler device corresponding to each output load, and each adapted to be connected to a corresponding output load, each of said coupler devices comprising: an electrically conductive coupling member supported in the region between the first and second electrically conductive members and having first and second spaced electrical terminal means;

first electrical path means in series with the first electrical terminal means and the corresponding output load; and

second electrical path means in series with the second electrical terminal means and including a dissipating means for dissipating electromagnetic energy applied thereto;

said electrically conductive coupling member and said first electrical path means being operable to extract and conduct electromagnetic energy from the region between the first and second electrically conductive members to the associated output load during the transmit mode of operation without application of a significant amount of electromagnetic energy to the second electrical path means or to the dissipating means included therein, and said electrically conductive coupling member and said first electrical path means being operable to conduct substantially all of the electromagnetic energy received by the associated output load during the receive mode of operation to the region between the first and second electrically conductive members; and

said first electrical path means, said electrically conductive coupling member, and said second electrical path means being operative to conduct a major portion of any electromagnetic energy reflected undesirably by the corresponding output load to the dissipating means, whereby such major portion of the reflected energy is dissipated in the dissipating means. 

1. A device for extracting electromagnetic energy from a region between a pair of concentric, electrically conductive cylinders and for conducting the energy to a load, and for dissipating a major portion of unwanted electromagnetic energy reflected by the load, comprising: an electrically conductive cylindrical coupling member supported in the region between the pair of spaced electrically conductive concentric cylinders and concentric therewith, and having first and second spaced electrical terminal means; first electrical path means in series with the first electrical terminal means and the load; and second electrical path means in series with the second electrical terminal means and including a dissipating means for dissipating electromagnetic energy applied thereto; said electrically conductive cylindrical coupling member and said first electrical path means being operable to extract and conduct electromagnetic energy from the region between the pair of electrically conductive cylinders to the load without application of a significant amount of energy to the second electrical path means or to the dissipating mean included therein; and said first electrical path means, said electrically conductive cylindrical coupling member, and said second electrical path means being operable to conduct a major portion of any electromagnetic energy reflected undesirably by the load to the dissipating means whereby such major portion of the reflected electromagnetic energy is dissipated in the dissipating means.
 2. A device in accordance with claim 1 wherein the dissipating means is a resistive load element.
 3. Apparatus for transferring input electromagnetic energy to a plurality of output loads for subsequent transmission in a transmit mode of operation and for processing electromagnetic energy received by said output loads in a receive mode of operation, and for dissipating electromagnetic energy reflected undesirably by said output loads, comprising: a first electrically conductive member having a plurality of openings provided therein in a plurality of groups each arranged around a common axis, each of said groups of openings having a number of openings differing from the number of openings of other groups; a second electrically conductive member spaced from the first electrically conductive member; said first and second electrically conductive members being arranged to receive in the region therebetween the the input electromagnetic energy; a plurality of coupler devices arranged in the plurality of openings provided in the first electrically conductive member, one coupler device corresponding to each output load, and each adapted to be connected to a corresponding output load, each of said coupler devices comprising: an electrically conductive coupling member supported in the region between the first and second electrically conductive members and having first and second spaced electrical terminal means; first electrical path means in series with the first electrical terminal means and the corresponding output load; and second electrical path means in series with the second electrical terminal means and including a dissipating means for dissipating electromagnetic energy applied thereto; said electrically conductive coupling member and said first electrical path means being operable to extract and conduct electromagnetic energy from the region between the first and second electrically conductive members to the asSociated output load during the transmit mode of operation without application of a significant amount of electromagnetic energy to the second electrical path means or to the dissipating means included therein, and said electrically conductive coupling member and said first electrical path means being operable to conduct substantially all of the electromagnetic energy received by the associated output load during the receive mode of operation to the region between the first and second electrically conductive members; and said first electrical path means, said electrically conductive coupling member, and said second electrical path means being operative to conduct a major portion of any electromagnetic energy reflected undesirably by the corresponding output load to the dissipating means, whereby such major portion of the reflected energy is dissipated in the dissipating means.
 4. An apparatus in accordance with claim 3 wherein each electrically conductive coupling member is a flat, multiedged element.
 5. An apparatus in accordance with claim 3 wherein each electrically conductive coupling member is a flat member having a circular configuration.
 6. An apparatus in accordance with claim 3 wherein the first and second electrically conductive members are flat members and each of the electrically conductive coupling members is a flat member.
 7. An apparatus in accordance with claim 3 wherein the first electrical path means in each coupler device includes: an output connector adapted to be connected to the associated output load; and an impedance-matching arrangement connected between the first electrical terminal means of the electrically conductive coupling member and the output connector for impedance matching the value of the impedance looking in the direction of the coupling member to the value of the characteristic impedance of the output connector.
 8. An apparatus in accordance with claim 7 wherein the impedance-matching arrangement includes impedance matching transformer sections.
 9. An apparatus in accordance with claim 8 wherein: the dissipating means included in the second electrical path means in each coupler device is a resistive load element; and wherein the second electrical path means further includes: an impedance-matching arrangement in series with the second electrical terminal means of the electrically conductive coupling member and the resistive load element for impedance matching the value of the impedance looking in the direction of the electrically conductive coupling member to the value of the resistive load element.
 10. An apparatus in accordance with claim 9 wherein the impedance-matching arrangement includes an impedance-matching transformer section.
 11. An apparatus in accordance with claim 10 further comprising: means associated with the first and second electrically conductive members for removing from the region between the first and second electrically conductive members any electromagnetic energy not extracted and conducted to associated output loads by the plurality of coupler devices.
 12. An apparatus in accordance with claim 10 wherein the second electrical path means in each coupler device further includes: a load-matching arrangement in series with the resistive load element for establishing an RF ground for the resistive load element and for eliminating substantially any reactance inherently present in the resistive load element.
 13. An apparatus in accordance with claim 12 wherein: the impedance-matching arrangement included in the first electrical path means and the impedance-matching arrangement and the load-matching arrangement included in the second electrical path means are formed from stripline components; and each coupler device further comprises: first and second flat opposing dielectric members arranged to enclose between opposing surfaces the stripline components; and first and second ground plane members in physical coNtact with the other surfaces of the first and second dielectric members, respectively.
 14. Apparatus for transferring input electromagnetic energy to a plurality of output loads for subsequent transmission in a transmit mode of operation and for processing electromagnetic energy received by said output loads in a receive mode of operation, and for dissipating electromagnetic energy reflected undesirably by said output loads, comprising: a first hollow, cylindrical, electrically conductive member having a plurality of openings provided therein in a predetermined pattern; a second hollow, cylindrical, electrically conductive member concentric with the first electrically conductive member; said first and second electrically conductive members being arranged to receive in the region therebetween the input electromagnetic energy; a plurality of coupler devices arranged in the plurality of openings provided in the first electrically conductive member, one coupler device corresponding to each output load, and each adapted to be connected to a corresponding output load, each of said coupler devices comprising: a hollow, cylindrical electrically conductive coupling member supported in the region between the first and second electrically conductive members and concentric with the first and second electrically conductive members, said electrically conductive coupling member having first and second spaced electrical terminal means; first electrical path means in series with the first electrical terminal means and the corresponding output load; and second electrical path means in series with the second electrical terminal means and including a dissipating means for dissipating electromagnetic energy applied thereto; said electrically conductive coupling member and said first electrical path means being operable to extract and conduct electromagnetic energy from the region between the first and second electrically conductive members to the associated output load during the transmit mode of operation without application of a significant amount of electromagnetic energy to the second electrical path means or to the dissipating means included therein, and said electrically conductive coupling member and said first electrical path means being operable to conduct substantially all of the electromagnetic energy received by the associated output load during the receive mode of operation to the region between the first and second electrically conductive members; and said first electrical path means, said electrically conductive coupling member, and said second electrical path means being operative to conduct a major portion of any electromagnetic energy reflected undesirably by the corresponding output load to the dissipating means, whereby such major portion of the reflected energy is dissipated in the dissipating means.
 15. Apparatus for transferring input electromagnetic energy to a plurality of output loads for subsequent transmission in a transmit mode of operation and for processing a electromagnetic energy received by said output loads in a receive mode of operation, and for dissipating electromagnetic energy reflected undesirably by said output loads, comprising: a first electrically conductive member having a plurality of openings provided therein in a plurality of concentric rings; a second electrically conductive member spaced from the first electrically conductive member; said first and second electrically conductive members being arranged to receive in the region therebetween the input electromagnetic energy; a plurality of coupler devices arranged in the plurality of openings provided in the first electrically conductive member, one coupler device corresponding to each output load, and each adapted to be connected to a corresponding output load, each of said coupler devices comprising: an electrically conductive coupling member supported in the region between the first and second electrically conducTive members and having first and second spaced electrical terminal means; first electrical path means in series with the first electrical terminal means and the corresponding output load; and second electrical path means in series with the second electrical terminal means and including a dissipating means for dissipating electromagnetic energy applied thereto; said electrically conductive coupling member and said first electrical path means being operable to extract and conduct electromagnetic energy from the region between the first and second electrically conductive members to the associated output load during the transmit mode of operation without application of a significant amount of electromagnetic energy to the second electrical path means or to the dissipating means included therein, and said electrically conductive coupling member and said first electrical path means being operable to conduct substantially all of the electromagnetic energy received by the associated output load during the receive mode of operation to the region between the first and second electrically conductive members; and said first electrical path means, said electrically conductive coupling member, and said second electrical path means being operative to conduct a major portion of any electromagnetic energy reflected undesirably by the corresponding output load to the dissipating means, whereby such major portion of the reflected energy is dissipated in the dissipating means. 